This invention relates to a carrier mechanism, and more particularly to a carrier mechanism of this kind, which carries out positioning between accommodating means and carrier means, thereby inserting an object, such as a recording medium, which has been carried by the carrier means, into the accommodating means, or taking the accommodated object, such as the recording medium, out of the accommodating means to the carrier means.
Conventionally, carrier mechanisms of this kind are known, for example, from Japanese Patent Laid-Open Publication Nos. Hei7-61523 and Hei10-91241. The conventional carrier mechanisms are for use in information reproducing apparatuses which each reproduces information recorded on a recording medium. FIG. 16A schematically shows the arrangement of one of the carrier mechanisms, for example, in which the carrier mechanism is formed of an accommodating rack 2 which can accommodate a plurality of recording media 1, a motor 3, a carrier section 4 driven for up-and-down movement by the motor 3, a control section 5 for controlling the rotational quantity of the motor 3, and a potentiometer 6 for detecting the position in height of the carrier section 4. A power supply terminal Vcc and a grounding terminal GND are connected to both ends of the potentiometer 6. Further, the potentiometer 6 has a sliding terminal 7 to which is linked one end of the carrier section 4.
When the carrier section 4 is moved up and down in order to take out the recording medium 1 accommodated in a desired position of the accommodating rack 2, or in order to newly insert the recording medium 1 into the desired position of the accommodating rack 2, the control section 5 determines a present position of the carrier section 4, based on a divided voltage VR generated at the sliding terminal 7, and calculates the difference between the desired position and the present position. Then, the control section 5 supplies a driving voltage VPWM of rectangular waves which have been pulse-duration modulated, to the motor 3, and moves the carrier section 4 in the vertical direction such that the difference between the desired position and the present position is eliminated.
More specifically, as shown in a waveform diagram of FIG. 16B, at an initial actuation of the driving section 4, a positive DC voltage VPWM is supplied to the motor 3, whereby the carrier section 4 is moved at an accelerated rate. Then, over a time period between time points t1 to t2, a driving voltage VPWM of rectangular waves is supplied to the motor 3, whereby the carrier section 4 is moved at a constant rate. Thereafter, over a time period between time points t2 to t3, a negative DC voltage VPWM is supplied to thereby decelerate the carrier section 4, and finally the driving voltage VPWM of rectangular waves is supplied to thereby move the carrier section 4 to the desired position, followed by stopping the carrier section 4.
In the conventional carrier mechanism as above, the driving force of the motor 3 is transmitted to the carrier section 4 by way of an actuator formed of a plurality of gears etc., to thereby move the carrier section 4 up and down.
The actuator formed of the gears etc. is a movable mechanism, so that it unfavorably has a very small amount of plays, looseness, etc. Therefore, although the motor 3 is electrically driven and controlled by the driving voltage V, which has been pulse-duration modulated, the actuator inevitably causes mechanical displacement in the movement of the carrier section 4, and therefore in some cases, the carrier section 4 cannot be positioned to the desired position.
Especially in the information reproducing apparatus provided with the accommodating rack 2 which accommodates the recording media 1, such as CD's (compact discs), downsizing of the apparatus becomes popular, and hence the plurality of recording media 1 must be accommodated tightly in the height direction.
Therefore, the carrier mechanism with extremely high accuracy has been demanded.
That is, the apparatus of this kind is prone to undertake a slight amount of vertical displacement between the carrier section 4 and the desired position due to plays, looseness, etc. Such displacement can make it impossible for the accommodated recording medium 1 from being smoothly taken out of the accommodating rack 2, or the carried recording medium 1 from being smoothly inserted into the accommodating rack 2, and can further cause a failure of the apparatus. Therefore, a carrier mechanism which can position the carrier section 4 to the desired position with high accuracy has been desired.